Demuxers already do this ...
Originally committed as revision 22796 to svn://svn.ffmpeg.org/ffmpeg/trunk
It is deduced from the AVStream values. */
int64_t start_time;
/** Decoding: duration of the stream, in AV_TIME_BASE fractional
- seconds. NEVER set this value directly: it is deduced from the
- AVStream values. */
+ seconds. Only set this value if you know none of the individual stream
+ durations and also dont set any of them. This is deduced from the
+ AVStream values if not set. */
int64_t duration;
/** decoding: total file size, 0 if unknown */
int64_t file_size;